Self-centering four-jaw chuck

Abstract

A chuck has a chuck body centered on and rotatable about a body axis, two first jaws diametrally flanking the body axis, each formed with an angled actuation face, and radially shiftable in the chuck body, and two second jaws diametrally flanking the body axis, each formed with an angled actuation face, interleaved with the first jaws, and radially shiftable in the chuck body. An inner sleeve engages the actuation faces of the first jaws and is axially shiftable to radially shift the first jaws, and an outer sleeve engages the actuation faces of the second jaws and is axially shiftable to radially shift the second jaws. An axially shiftable actuation element carries a pivotal force-transmitting rocker having inner and outer ends operatively engaging the respective inner and outer sleeves for axially shifting the inner and outer sleeves on axial shifting of the element while permitting limited axial movement of the inner and outer sleeves relative to each other.

1 . A chuck comprising: 
 a chuck body centered on and rotatable about a body axis;    two first jaws diametrally flanking the body axis, each formed with an angled actuation face, and radially shiftable in the chuck body;    two second jaws diametrally flanking the body axis, each formed with an angled actuation face, interleaved with the first jaws, and radially shiftable in the chuck body;    an inner sleeve engaging the actuation faces of the first jaws and axially shiftable to radially shift the first jaws;    an outer sleeve engaging the actuation faces of the second jaws and axially shiftable to radially shift the second jaws;    an axially shiftable actuation element; and    means including a force-transmitting rocker pivotal on the actuation element and having inner and outer ends operatively engaging the respective inner and outer sleeves for axially shifting the inner and outer sleeves on axial shifting of the element while permitting limited axial movement of the inner and outer sleeves relative to each other.    
   
   
       2 . The chuck defined in  claim 1  wherein the chuck body forms a pressurizable chamber and the actuation element is a sleeve having a collar forming a piston in the chamber.  
   
   
       3 . The chuck defined in  claim 2  wherein the actuation-element sleeve is coaxial with and between the inner and outer sleeves.  
   
   
       4 . The chuck defined in  claim 3  wherein the inner and outer sleeves respectively have outer and inner cylindrical surfaces sliding on the actuation-element sleeve.  
   
   
       5 . The chuck defined in  claim 4  wherein the outer sleeve has an outer cylindrical surface sliding on the chuck body.  
   
   
       6 . The chuck defined in  claim 1  wherein the jaws are releasably mounted on the inner and outer sleeves.  
   
   
       7 . The chuck defined in  claim 1  wherein the rocker extends generally radially and has a center part pivoted in the actuation element, an outer end part pivoted in the outer sleeve, and an inner end part pivoted in the inner sleeve.  
   
   
       8 . The chuck defined in  claim 7  wherein the center part pivots about a rocker axis lying generally in a plane perpendicular to the body axis and tangential to a circle centered on the body axis and lying in the plane.  
   
   
       9 . The chuck defined in  claim 7  wherein the center part of the rocker has a part-spherical outer surface.  
   
   
       10 . The chuck defined in  claim 6  wherein the end parts of the rocker have part-spherical outer surfaces.  
   
   
       11 . The chuck defined in  claim 7  wherein the inner and outer sleeve and actuation element are formed with radially throughgoing generally cylindrical bores holding the respective parts of the rocker.  
   
   
       12 . The chuck defined in  claim 1  wherein there a plurality of such rockers angularly distributed about the sleeves.  
   
   
       13 . The chuck defined in  claim 1 , further comprising 
 an elastic seal engaged around the jaws.    
   
   
       14 . The chuck defined in  claim 13  wherein the seal is vulcanized to the jaws.